Male-to-female intimate partner violence accounts for 26 percent of violence-related injuries in women presenting in hospital emergency departments and 33 percent of all female homicides. Adolescence provides an excellent "window of opportunity" for the prevention of intimate partner violence. Patterns of relating in intimate relationships are still relatively undifferentiated and open to influence. However, the evidence supporting traditional, school-based programs for the prevention of teen dating violence is mixed. A major problem with existing programs is that they are "one size fits all," making it difficult to meet the diverse needs of students boys and girls, individuals who are dating and those who are not, individuals who have experienced dating violence as a victim, perpetrator, or both, and those who have not. Perhaps most importantly, these interventions neglect individual differences in readiness to use healthy, non-violent ways of relating to stay violence-free. In Phase I the objective was to use expert system technology to integrate best practices for teen dating violence prevention with the Transtheoretical Model (TTM), the "stage model," to develop an interactive, multimedia computer-administered change program that delivers individualized intervention sessions and exercises tailored to stage of change and other individual characteristics. In Phase II, the objective is to complete development of the intervention package and assess its efficacy in a randomized clinical trial involving 4,000 teens from 20 Illinois high schools. Efficacy will be assessed by comparing the intervention and control groups on dating violence victimization and perpetration, frequency of skill use, attitudes supporting dating violence, and several secondary outcome measures. Public Health Relevance: The proposed project is the first to develop a multimedia, computer-administered teen dating violence prevention program based on an empirically validated model of behavior change, the Transtheoretical Model. The program delivers interventions tailored to individual dating history, dating violence experiences, gender, and stage of change for using healthy relationship skills to stay violence free. The intervention has the potential to reduce and prevent teen dating violence and it physical and emotional consequences, and improve the lives and relationships of teens now and in the future.